Image encoding and decoding method and device for limiting partition condition of chroma block, and method for transmitting bitstream

Abstract

An image encoding/decoding method and apparatus are provided. An image decoding method performed by an image decoding apparatus includes determining a splitting type of a current block, splitting the current block into a plurality of lower-layer blocks based on the splitting type, and decoding the lower-layer blocks. In this case, the current block may be a chroma block, and the determining the splitting type of the current block may be performed by disallowing a predetermined splitting type having a width or height of the lower-layer blocks being a predetermined value, among a plurality of splitting types.

1 . An apparatus for image decoding, the apparatus comprising:
 a memory; and   at least one processor connected to the memory, the at least one processor configured to:   determine whether a predetermined splitting type is allowed for a first block;   determine a splitting type for the first block based on whether the predetermined splitting type is allowed for the first block;   obtain a second block by splitting the first block based on the determined splitting type;   generate prediction samples by performing prediction for the second block based on prediction information; and   reconstruct the second block based on the generated prediction samples,   wherein, based on a tree structure of the first block being a dual tree structure and a width of a chroma block derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is not allowed for the first block regardless of a height of the chroma block, and   wherein, based on a tree structure of the first block being a dual tree structure and a height of a chroma block with a width greater than  4  derived from the first block by the predetermined splitting type being  2 , the predetermined splitting type is allowed for the first block.   
     
     
         2 . The image decoding apparatus of  claim 1 , wherein the predetermined splitting type includes at least one of a vertical binary splitting type or a vertical ternary splitting type. 
     
     
         3 . The image decoding apparatus of  claim 1 , wherein, based on the predetermined splitting type being allowed for the first block, a width of the first block is greater than a predetermined first value. 
     
     
         4 . The image decoding apparatus of  claim 3 , wherein the predetermined first value is determined differently based on the predetermined splitting type. 
     
     
         5 . The image decoding apparatus of  claim 1 , wherein, whether the predetermined splitting type is allowed for the first block is determined based on whether a number of times of splitting the first block from a quadtree leaf node is equal to or greater than a predetermined threshold value. 
     
     
         6 . The image decoding apparatus of  claim 1 , wherein, based on the predetermined splitting type being determined as the splitting type for the first block, a width of the second block is equal to or greater than 4. 
     
     
         7 . An apparatus for image encoding, the apparatus comprising:
 a memory; and   at least one processor connected to the memory, the at least one processor configured to:   determine whether a predetermined splitting type is allowed for a first block;   determine a splitting type for the first block based on whether the predetermined splitting type is allowed for the current block;   obtain a second block by splitting the first block based on the determined splitting type;   generate prediction samples by performing prediction for the second block based on prediction information; and   encode the second block based on the generated prediction samples,   wherein, based on a tree structure of the first block being a dual tree structure and a width of a chroma block derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is not allowed for the first block regardless of a height of the chroma block, and   wherein, based on a tree structure of the first block being a dual tree structure and a height of a chroma block with a width greater than 4 derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is allowed for the first block.   
     
     
         8 . The image encoding apparatus of  claim 7 , wherein the predetermined splitting type includes at least one of a vertical binary splitting type or a vertical ternary splitting type. 
     
     
         9 . The image encoding apparatus of  claim 7 , wherein, based on the predetermined splitting type being allowed for the first block, a width of the first block is greater than a predetermined first value. 
     
     
         10 . The image encoding apparatus of  claim 9 , wherein the predetermined first value is determined differently based on the predetermined splitting type. 
     
     
         11 . The image encoding apparatus of  claim 7 , wherein whether the predetermined splitting type is allowed for the first block is determined based on whether a number of times of splitting the first block from a quadtree leaf node is equal to or greater than a predetermined threshold value. 
     
     
         12 . The image encoding apparatus of  claim 7 , wherein, based on the predetermined splitting type being determined as the splitting type for the first block, a width of the second block is equal to or greater than 4. 
     
     
         13 . An apparatus for transmitting data for an image, the apparatus comprising:
 at least one processor configured to obtain a bitstream; and   a transmitter configured to transmit the bitstream, wherein the bitstream is generated by an image encoding method, the image encoding method comprises:   determining whether a predetermined splitting type is allowed for a first block;   determining a splitting type for the first block based on whether the predetermined splitting type is allowed for the current block;   obtaining a second block by splitting the first block based on the determined splitting type;   generating prediction samples by performing prediction for the second block based on prediction information;   encoding the second block based on the generated prediction samples into a bitstream; and   transmitting the data comprising the bitstream,   wherein, based on a tree structure of the first block being a dual tree structure and a width of a chroma block derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is not allowed for the first block regardless of a height of the chroma block, and   wherein, based on a tree structure of the first block being a dual tree structure and a height of a chroma block with a width greater than 4 derived from the first block by the predetermined splitting type being 2, the predetermined splitting type is allowed for the first block.